Climb Real Estate, a boutique San Francisco brokerage focused on city-dwelling Millennials, has been acquired by NRT LLC, the nation’s largest residential brokerage, the companies announced Wednesday.NRT is the parent of Coldwell Banker, Sotheby’s International Realty and ZipRealty and a subsidiary of Realogy, a publicly traded real estate conglomerate.NRT has pursued the same approach with other regional firms it acquired including the Corcoran Group in New York City and Laura McCarthy Real Estate in St. Louis, said Bruce Zipf, NRT’s president and chief executive.Climb tries hard to appeal to Millennials by focusing on mobile technology and social media.“I believe what this represents is a more traditional type platform coming together with a more innovative, unique-type platform” and providing the financial capital to expand Climb in the Bay Area, Zipf said.Greg Macres, NRT’s executive vice president for the western region, said, We want our agents to be more mobile (and) stretch the boundaries of technology.